Soft-field sensing, such as Electrical Impedance Tomography (EIT) (also referred to as Electrical Impedance Spectroscopy (EIS)), diffuse optical tomography, elastography, and related modalities may be used to measure the internal properties of an object, such as the electrical properties of materials comprising internal structures of an object (e.g., a region of a human body). For example, in EIT systems, an estimate is made of the distribution of electrical conductivities of the internal structures, such as within a patient. These EIT systems reconstruct the conductivity and/or permittivity of the materials within the area or volume based on an applied excitation (e.g., current) and a measured response (e.g., voltage) acquired at a surface of the area or volume. Visual distributions of the estimates can then be formed.
The EIT measurements may be obtained by applying excitations, which are often very small electrical currents or voltages, using for example skin-contacting electrodes, and measuring the resulting voltages or currents on the same or on different skin-contacting electrodes. The excitations are typically pre-computed and applied to a configuration of transducers coupled to a surface of an object, which is highly dependent on a configuration of the transducers. Presently, the use of EIT electrodes requires a dedicated transducer set in a predetermined geometry, such as a circumferential belt of electrodes surrounding the thorax. Attaching sets of electrodes in predetermined geometries is often problematic in clinical settings where the patient cannot be manipulated appropriately. Further, the need for dedicated electrode arrays presents an additional clinical burden to the caregiver, cost burden to the hospital, insurer, and/or patient, and results in additional discomfort to the patient.